Control mechanism



April 14, 1959 A. J. WELCH CONTROL MECHANISM 3 SheetS- Sheet 1 FiledMarch 5, 1956 N l i i ,J

fnz/erzi'a'r' Qri/Lur J Z06 Zak J' April 14, 1959 A.-.J. WELCH' CONTROLMECHANISM 3 Sheets-Sheet 2 Filed March -5, 1956 A. J. WELCH CONTROLMECHANISM April 14, 1959 Filed March 5, 1956 3 Sheets-Sheet 5 WWW m NNWW mwN fnuenfbr Q'rikur'JZZ/ek/o @8844 ujm United StatesPatent Q.

CONTROL NIECHANISM Arthur J. Welch, Oak Park, Ill., assignor toBorg-Warner Corporation, a corporation of Illinois Application March 5,1956, Serial No. 569,544 16 Claims. (Cl. 19282) This invention relatesto a thermally responsive control mechanism, and more particularly to athermally responsive control mechanism suitable for controlling theoperation of a fan employed in an automotive vehicle.

The desirability of having suitable mechanism for effecting theconnection and disconnection of an automotive vehicle fan to the sourceof driven power has long been recognized. A great many attempts havebeen made in the past to provide a suitable mechanism to drive the fanwhen it was needed, but disconnect the fan when it was not required.Most of such prior attempts have, to the best of my knowledge, beencommercially unfeasible-except for a few special situations in whichcost was not an important factor-because the mechanism was tooexpensive, functionally undependable or lacked adaptability to thevarying circumstances under which automotive vehicles operate.Furthermore, most of these prior attempts to provide a desirablecontrolled fan mechanism require that extensive changes be made in othercomponents of the vehicle in which the fan was to be disposed.

It is therefore one of the objects of the present invention to provide anew and improved control mechanism particularly suited to control theoperation of a fan in automotive vehicles which overcomes the defects inthe above discussed prior devices. Another object is the provision ofthe device in accordance with the preceding object which is inexpensive,dependable, adjustable and which requires almost no modificationwhatsoever of the other components of modern automotive vehicles. 7

It is another object of the present invention to provide a new andimproved fan control mechanism for automotive vehicles which comprises aunitary assembly which is readily attached to the conventional pumpshaft employed in automotive vehicles the unitary assembly beingattached to the pump shaft in exactly the same manner as now employed toeffect the installation of the conventional fan assembly.

A further object of the present invention is the provision of a new andimproved fan control mechanism of a highly simplified nature in whichthe operating characteristics thereof are readily adjustable withoutrequiring the disassembly of the device.

Other objects and features of the invention will be readily apparent tothose skilled in the art'from the specification and appended drawingsillustrating certain preferred embodiments in which:

Figure 1 is a front elevational view of a device incorporating theprinciples of the present invention, with parts broken away tofacilitate the showing, illustrating the fans operating condition;

Figure 2 is a sectional view along the plane of line 22 of Figure 1,taken when the fan is not operating;

Figure 3 is a partial end sectional view along the plane of line 3-3 ofFigure 1;

Figure 4 is a front elevational view, with parts broken away tofacilitate the showing of a modified form of the invention, illustratingthe fans operating condition;

Figure 5 is a sectional view along the plane of line 5-5 of Figure 4,taken when the fan is not operating; Figure 6 is a side elevational viewshown in section of a further modified form of the present invention;

Figure 7 is a view along the plane of line 7-7 of Figure 6.

Turning first to the preferred form of the invention as illustrated inFigures 1 to 3, there is illustrated a conventional pump shaft 1conventionally journaled by bearing means 2 to the fixed housing 3. Pumpshaft 1 is driven by means of a pulley member 4 which is rotated by aconventional fan belt 5, the latter being driven by the engine (notshown) of the vehicle in the usual manner. The pulley member 4 includesan integral cup shaped member 6 having a radially inwardly extending,.

circular portion 7, as shown in Figure 2. The portion 7 is provided witha plurality of circumferentially spaced openings 8 adapted to receivefastening means.

The inner surface of the portion 7 defines a generally circular openingthrough which extends a support member, indicated in general by thenumeral 9, of cast iron, a phenolic resin, or other suitable material.The support member 9 has a central circular portion and a forwardlyfacing, radially extending surface 10. Member 9 is further provided witha plurality of outwardly projecting arms 11, disposed inwardly of theaforementioned' circular opening defined by the inner surface of portion7. The arms 11 are provided with suitable,

threaded openings 12 therein which register with the openpress-fit ontothe end of pump shaft 1, the outermost end of the pump shaft abutting aninternal wall defining the outer end of this innermost portion of theopening 15. The forward portion of opening 15 is threaded, and insertedtherein is a suitably threaded stud.

As a result of the aforedescribed construction, the support member 9 andthe pulley member 4 are fixed together; the support member 9, inaddition, is fixed to the outer end of the pump shaft 1. It willtherefore be seen that when the vehicle engine operates to drive the fanbelt 5, the pulley member 4, the support member 9 and pump shaft 1 willrotate together.

The outermost end of support member 9 is provided with a plurality ofexternal screw threads 16 whichpreferably are acme stub threads of 3 perinch. Mounted upon the outer end of the support member 9 is a nut 17 ofsteel, phenolic resin, or other suitable material having threads 18complementary to-and associated withthe threads on the support member 9.The threads 16 and 18 are constructed and arranged to be left handthreads, and preferably are self-locking. The nut 17 is generallycircular in outer configuration, and has a rearwardly facing, radiallyextending friction face 17 To the nut 17 there is fixedly attached, bymeans of a rivet 19, one end of a spirally wound bimetal 21. The

J opposite end of the bimetal 21 is provided with a threaded opening 22;cooperating with this opening is a stud 23 which serves to fix thebimetal 21, in a manner to be hereinafter described, to a cup shapedmember 24. It should be noted that bimetal 21 projects forwardlyto theright in Figure 2-beyond the forward face of nut 17 and almost intoengagement with cup 24, whereby Patented Apr. 14, 19,59?

locking of nut 17 at the most forward end of threads 16 is prevented.The outermost end of the support member 9 is provided with anon-circular exterior portion upon which the cup 24-which has acentrally disposed, complementary non-circular portion -is supported,

24 is rotated with the support member 9, the scoops 27 will force airinwardly of the cup 24 and into engagement with bimetal 21.

It will be obvious that the degree of initial tension applied to thebimetal 21 is determined by the positioning of the ends thereof. Meansare provided to vary this initial tensioning, for a purpose to besubsequently described, which include the aforementioned stud 23 and aslot 28 extending around approximately 60 degrees of the outer surfaceof the cup 24. In Figures 2 and 3 it will .be seen that the stud 23.extends through this slot 28, and when loosened may be positioned asdesired along the length of the slot 28 and subsequently retightened tofix the end of the bimetal associated therewith in any position alongthe length of the slot 28.

Carried by the support member 9 between the surface 10 thereof and thenut 17' thereon is a fan support member 31 which is generally cruciformin configuration and formed of aluminum, cast iron, or other suitablematerial. The member 31 has a rearwardly facing, radially extendingsurface 31 as illustrated in Figure 2. (If desired, a belleville springmay be disposed on support member 9 between surface 31 and surface 10.)The fan support member 31 is rotatably disposed about the support member9 upon suitable nylon or needle bearings 32 and maintained againstforward movement by means of a retainer ring 33. The member 31 has anannular, forwardly extending projection 34 which is provided with aforwardly facing, radially extending friction surface 34. The radiallyouter surface of projection 34 extends through suitable circularopenings in a pair of crossed fan blades together forming a fan bladeassembly 35. To the inner surface of this fan blade assembly there isfixedly mounted, as by welding, a steel strengthener ring 36 having aplurality of spaced, circumferentially elongated slots therein. Disposedbetween the ring 36 and the projection 34 are a pair of washer means 37.

The fan blade assembly 35, as best illustrated in Figure 1, is providedwith a plurality of spaced, circumferentially elongated slots 38inregistration with the slots in the ring 36-and extending through each ofthose slots is a stud 39, the inner end of which is received in one of aplurality of suitably threaded openings 41 in the fan support member 31.The studs 39, although preventing forward movement of the fan bladeassembly 35, permit rotational movement thereof relative to the fansupport member 31 to the degree determined by the length of the-slots inthe fan blade assembly 35' and strengthener ring 36.

\ When the device is disposed in an automobile, it is aligned with andimmediately behind the rear face of the radiator of the vehicle,indicated by the numeral 42 in Figure 2. When the vehicle engine isoperating the fanbelt will be continually driven so to effect constant,common rotation of pulley 4, support member 9, the pump shaft 1, cup 24and nut 17. This rotation would conventionally be clockwise when viewedfrom the front, (the right end as illustrated in Figure 2). In thecondition of the device illustrated in Figure 2, the fan support member31 and the fan blade assembly 35 would rotate in the same generaldirection as the support memher 9- because of the slight bearing dragbetween the support member 9 and the fan support member 31;

I with the vehicle moving forwardly (toward the right in Figure 2) thefan support member 31 and the fan blade assembly 35 would also tend torotate in the clockwise direction with the support member 9 because thepitch of the fan blades is such that as the air moves rearwardly pastthese blades, clockwise motion thereof is induced. The fan support 31and the fan blade assembly 35 are, however, merely windmilling, and arenot ab- T. sorbing any significant amount of power from the engine,

inasmuch as fan support member 31 is not fixedly connected with any ofthe elements being drivendirectly or indirectly-by the engine.

With the vehicle moving forwardly, air will pass :I through the radiator42 and increase in temperature in nut 17 and the'surface 34' on the fansupport member 31 will engage. Inasmuch as the fan support member 31 isrotating more slowly than the remainder of the assembly when the surface17' and 34' are brought into frictional engagement by the bimetal 21,rotation of the 1 nut 17 will continue in the same direction and furtherrearward movement thereof will result. The nut 17 will force the fansupport member rearwardly so that the surface 31 thereof will engage thesurface 10 on the support member 9. (As previously indicated abelleville spring may be disposed between those surfaces; if such aspring is utilized, surface 31' will compress the spring betweensurfaces 10 and 31' to effect a cushioned engagement.) When this occurs,it will be seen that the fan support member 31 is clamped between thesurface 10 on the fan support member 9 and the surface 17 on nut 17 sothat the member 31 is mechanically connected to-and will rotate with-thefan support member 9.

As previously indicated, the fan blade assembly 35- has a rotationalmovement permitted to it, relative to the support member 31, determinedby the length of the slots 38. As a result, when the support member 31begins to rotate with the support member 9 and the pump shaft 1, therelative position of the studs 39 in the slots- 38 will move from thatindicated in dotted lines in Figurel to that indicated in full lines inthat figure. The studs 39 will then ensure common rotation of the fanblades 35 with their support member 31. In this condition of the device,all of the parts are locked up and rotate together so. that there are noparts moving relative to the other parts. As a result, wear iseliminated and the fan operates in substantially the same way asit-do'es in conventional automotive vehicles. I

When the rotative speed of the shaft 1 rapidly decreases, as when theaccelerator of the vehicle is released rapidly, the momentum of the fanblade assembly 35 will causeit to attempt to continue rotation at theprevious high speed of shaft 1, the fan blade assembly 35, therefore,will be rotating faster than the shaft 1 and the support member 9. As aresult, the fan blade assembly 35 will rotate relative to the supportmember 9 and the fan. support member 31 to the degree permitted by theslots 38; in other words, the fan blades will rotate relative to thesupport member until the studs 39 once again occupy the relativeposition in the slots 38 indicated by the. dotted lines in Figure l. Thefan blades 35 will in that. instant effect a substantial impact upon thestuds 39 which will be transmitted to the fan support member 31-Inasmuch as the to effect clockwise rotation thereof. fan support member31 and the nut 17 are in frictional engagement at this time, nut 17' ismoved in a clockwise direction with respect to the support member 9 sothat the nut 17 tends to move away from the fan support member 31 andeffect its reiease. If the bimetal 21 is at this time still hot, nut 17will immediately be returned to its frictional engagement position withthe fan support member 31; when the shaft 1 again overspeeds the fan, aspreviously described, the fan will once again be locked up so as torotate with the shaft 1.

It should be noted thatthe bimetal 21 will not have enough strength inand of itself to move the nut 17 away from the fan support member 31during this locked up condition of the device because of theself-locking effect of the frictional engagement between nut 17 and thefan support member 31. However, if the bimetal 21 is sufficiently cooland the shaft 1 speed decreases rapidly, when the fan blade assembly 35strikes the studs 39 to effect rotation of the fan support member 31, aspreviously described, in the direction to effect movement of the nut 17forwardly, as the nut 17 begins this forward movement the bimetal 21will continue this movement to the end that frictional engagementbetween the nut 17 and the fan support member 31 is broken and notreestablished. As a result, the normal condition of the device aspreviously described will obtain, and the fan support member 31 and thefan blades 35 will be released from their locked up connection with theshaft 1 and will windmill and no longer absorb any more than aninsignificant amount of power from the engine.

It will be obvious of those skilled in the art that the operatingtemperature at which the nut 17 is moved into engagement with the fansupport member 31 may be varied by changing the initial tension oflthebimetal 21. As previously indicated, this is accomplished in the presentinvention by the stud 23 and its positioning within the slot 28. If theoperating temperature of the device is to be increased or decreased, itis only necessary to loosen the stud 23 from its normal tight positionof frictional engagement with the cup 24. When the stud 23 is loosened,it may be positioned as desired within the slot 28 and movement of thestud 23 will of course effect movement of the end of bimetal 21 in whichthe stud 23 is threaded. When the stud 23 is once again retightened sothat the head portion thereof and the asso ciated end of the bimetal areonce again in tight frictional engagement with cup 24, the device willoperate in the manner aforedescribed. It should be noted that thischange in operating temperature may be effected very readily withoutmodifying any of the elements of the device or effecting theirdisassembly. If desired, suitable indicia may be provided on the cup 24indicating the direction in which the stud 23 is to be moved to eitherincrease or decrease the operating temperature of the device.

Turning now to a consideration of the embodiment of the inventionillustrated in Figures 4 and 5, there is a pump shaft 101 suitablyjournaled by bearings 102 in a fixed member in conventional fashion.Fixedly mounted upon the pump shaft 101 is a pulley 103 driven by' anengine driven fan belt 104, the fan belt effecting common rotation ofthe pulley 103 and the pump shaft 101. The front portion of the pulley103 is provided with a radially extending surface 105.

The front portion of the pump shaft 101 is keyed 'at 106 to a stud 107which rotates with the shaft 101. The outer periphery of the stud 107 isprovided with acme threads 108 which cooperate with threads 109 on a nut111 which is rotatable upon the stud 107 and consequently longitudinallymovable with respect to the shaft 101. The threads 108 and 109 are lefthanded and are of the self locking variety.

The outer periphery of the nut 111 has attached thereto by suitablemeans, such as a rivet, one end of a spirally wound bimetal 112, theopposite end of which is attached to a stud 113 by means of a generallyU- shaped clip The stud and clip 114 attach the associated end of thebimetal 112 to one portion of a cup shaped member also keyed to theshaft 101 for rotation therewith. A stud 116 extends into a suitablethreaded opening in the outer end of the pump shaft 101 to hold the cup115, the stud 107, and the nut 111in position on the shaft 101. As aresult, and as a result of the connection of these elements previouslydescribed, they all rotate together with the pump shaft 101 at alltimes. As best illustrated. in Figure 4, the upper portion of the cup115 is provided with an elongated slot 117 so that the initialtensioning on the bimetal 112 may be adjusted, as previously described,by moving the stud 113 to a desired position within the slot 117. Thefront face of the cup 115 is provided with a plurality of windows 118formed by scoops 119 sheared from the front face of the cup, the scoopsdirecting heated air which passes through a vehicle radiator 120 into.the interior of the cup 115 and into engagement with the bimetal 112.

Rotatably supported on the shaft 101 by suitable bearings is a fansupport member 121 having a rear, radially extending face 122 and afront, radially extending fric tion face 123. (If desired, a bellevillespring may be disposed upon shaft 101 adjacent face 122 and surface105.) As best illustrated in Figure 5, the surface122 is adapted forengagement with the surface 105 on the pulley 103 while the surface 123is adapted to engage a radially extending friction surface 124 formingthe rear portion of the nut 111. The fan support member 121 carries afan blade assembly 125 comprising a pair of crossed fan blade members.The fan blade assembly 125 has a circular aperture centrally locatedtherein which fits over a forwardly extending annular portion 126 on thesupport member 121. The fan blade assembly 125 has welded to the rearface thereof an annular member 127, the fan blade assembly 125 and theannular member 127 having registering openings 128 extendingtherethrough. Through each of these openings 128 extends a bolt 129, theopposite end of which is received in a threaded aperture 131 in the fansupport member 121. As illustrated in Figures 4 and 5, the bolts 129permit rotation of the fan blade assembly 125 relative to the fansupport member 121 to a degree defined by the circumferentially facingends of the slots 128.

The operation of the device of the present invention illustrated inFigures 4 and 5 will be readily apparent to those skilled in the art,this operation being substantially identical with the previouslydescribed operation of the device illustrated in Figures 1 through 3.

The mechanism for effecting adjustment of the initial bimetal tension inFigures 4 and 5 is such that it is unnecessary to provide a threadedopening in the end of bimetal 112. This opening through the end of thebimetal 112 need only be sufficiently large to permit the stem of stud113 to pass therethrough; the underside of I the head of stud 113 thenengages the uppermost surface of the U-shaped clip 114, while theopposite end of the stud 113 is threadably engaged in a suitablethreaded aperture in the opposite leg of the U-shaped clip 114.

The aforedescribed embodiments of the present invention are useful insubstantially all of the present day automotive vehicles of thepassenger car type, whether such vehicles are manually shifted, employfluid couplings, The embodiment of the or employ torque converters.present invention illustrated in Figures 6 and 7 is particularlysuitable, however, in automotive vehicles in which the speed of theengine changes relatively rapidly; such conditions prevail inautomobiles, for example, having manually shiftable means or fluidcouplings. In this embodiment there is illustrated the pump shaft 1,previ ously described, suitably journalled by the bearing means 2 in thefixed means 3. There is further provided pulley means 204 driven by theconventional fan belt 5, the

pulley means 204 comprising an integral cup member 6 having the radiallyinwardly extending, circular portion 7,

as previously described with respect to the embodiment shown in Figure2. The portion 7 is provided with a plurality of circumferentiallyspaced openings 8.

. The inner surface of the portion 7 defines a generally circularopening through which extends a support member 209 of cast iron, aphenolic resin, or other suitable material. The support member 209 has acentral circular portion with a forwardly facing, radially extendingsurface 210. The member 209 is further provided with a plurality ofoutwardly projecting arms 211, disposed inwardly of the aforementionedcircular opening defined by the inner surface of portion 7. The arms 211are provided witha plurality of suitable, threaded openings 212 thereinwhich respectively register with the openings 8 in the portion 7.Suitable studs 213 respectively extend through the openings 8 andthreadably engaged with the openings 212 so as to fix the member 209 tothe portion 7.

The support member 209 includes a forwardly projecting portion 214having an opening 215 extending therethrough. The opening 215 is dividedinto sections of different diameters, the innermost of which is circularand is press fit onto the end of pump shaft 1, the inner? most end ofthe pump shaft abutting an internal wall defining the outer end of thisinnermost portion of the opening 215. The forward portion of opening 215may be threaded to receive a suitable threaded stud.

As a result of the aforementioned construction, the support member 209and the pulley member 204 are fixed together; the support member 209, inaddition, is fixed to the outer end of the pump shaft 1. It willtherefore be seen that when the vehicle engine operates to drive the fanbelt 5, the pulley member 204, the support member.209, and pump shaft 1will rotate together.

The outermost end of support member 209 is provided with a plurality ofintegral external screw threads 216 which preferably are acme studthreads of three per inch.

Mounted upon the outer end of the support member 209 there is a nut 217of steel, phenolic resin or other suitable material having threads 218,complementary to-- and, associated with-the threads 216 on the supportmember 209. The threads 216 and 218 are constructed and arranged to beleft-hand threads, and preferably are self-locking. The nut 217 iscircular in outer con.-

figuration, and has a rearwardly facing, radially extending frictionface 217'.

To the nut 217 is fixedly attached, by means of a rivet 219, one end ofa spirally wound bimetal 221. The opposite end of the bimetal 221 isprovided with an opening 222; co-operating with this opening is a stud223 which carries a nut 224. The stud 223 and the nut 224 serve to fixthe bimetal 221 to the before described cup shaped member 24. The cupshaped member 24 is keyed to the outer end of the support member 209 inthe same Way as before described with respect to the cup 24, and thesupport member 9 of Figure 1. The initial tension of the bimetal 221 maybe varied by moving the stud 223 in the slot 28 provided in the cup 24,as previously described.

Carried by the support member 209' is a fan support member 231 rotatablymounted upon the support member 209 by means of suitable bearings 232.The member 231 has a forwardly facing, radially extending frictionsurface 234, radially outwardly of which is an annular recessed surface235 which extends radially outwardly and against which is disposed therear face of a fan blade assembly 236, comprising a pair of crossed fanblades.

Fan blade assembly 236 is provided with a plurality of spaced openings237 which respectively register with a plurality of spaced threadedopenings 238 in the fan support member 231. A stud 239 projects througheach of the openings 237', and is in threaded engagement with thethreaded portion of the openingv238 associated therewith, so as to holdthe fan blade assembly 236 on the fan support member 231. The dimensionof stud 239 is such as to fill the associated opening 237 so that norelative motion between the fan blade assembly 236 and the fan supportmember 231 may occur. Keyed to the rear surface of the fan supportmember 231 by cooperating non-circular surfaces is a belleville spring241 which is generally circular. The spring 241 has a central,noncircular opening therein which receives a milled keyway on the rearsurface of the fan support member 231; the spring 241 has lugs 242extending, rearwardly of the spring 241 and into cooperating openings243 formed in a thrust washer 244. The thrust washer 244 is generallycircular in configuration and is formed of bronze or any other similarsuitable material; the central portion of the washer 244 is providedwith a circular opening which rotatably seats upon a circular seat 245formed on the. support member 209.

As a result of this arrangement it will be seen that the fan bladeassembly 236 will rotate with the fan support member 231; the bellevillespring 241 will also turn with the fan support member 231, and thethrust washer 244. will rotate with the belleville spring 241 in view ofthe cooperation between the lugs 242 and the openings 243.,

When the device is disposed in an automobile it is aligned with, andimmediately behind, the. rear face of the vehicle radiator, indicated bythe numeral 246 in Figure 6. When the vehicle engine is operated, thefanv belt 5 will be continually driven so. as to effect constant, commonrotation of the pulley 204, support member 209, the pump shaft 1, cup 24and nut 217. This rotation will conventionally be clockwise when viewedfrom the front, or the right side as illustrated in Figure 6. In thecondition of the device illustrated in Figure 6, the fan support 231 andthe fan blade assembly 236, will rotate in the same direction as member209 because of the slight bearing drag between the support member 209and the fan support member 231; when the vehicle is moving forwardly(toward the right in Figure 6) the fan support member 231 and the fanblade assembly 236 willalso tend to rotate in the clockwise direction,because.

the pitch of the fan blades is such that as air moves rear- Wardly pastthese blades, clockwise motion thereof isinduced. The fan support member231 and the fan blade assembly 236 are, however,,merely wind-milling.

When the temperature of the air surrounding the device is suflicientlyincreased, for example when heated air passes rearwardly from theradiator 246, and the.

temperature of bimetal 1-21 is increased sufficiently, it

will force rotation of the nut 217 in a counterclockwise Uponv directionto eifect rearward movement thereof. sufiicient rearward movement of thenut 217, the rear friction face 217' thereon will engage the forwardlyfacing friction surface 234 of the fan support member 231.. Inasmuch asthe fan support member 231 is rotating more. slowly than the nut, 217,when this engagement occur rotation of the nut 217 Will be forced tocontinue in the same direction, and further rearward movement thereof 1will result. The nut 217 will force the fan support member 231rearwardly against the bias of the belleville spring- 241 until themember 231 is fixedly clamped. in a sand.- wich comprising the thrustWasher 244, the spring 241, the fan support member 231 and the nut217 sothat this entire assembly rotates together. In other words, all of theseelements will rotate together, and at the same speed as the pulley means204 and pump shaft 1. The device then operates substantially as the fansin present day vehicles.

With the device in this locked up condition, when the relative speed ofthe pulley means 204 rapidly decreases, as when the accelerator of thevehicle is released rapidly, the momentum of the fan blade assembly 236will cause it to attempt to continue rotation at its previous highspeed. The fan blade assembly 236, and the fan support member 231attached thereto, willtherefore be rotating faster then the pulley means209. As a result, the nut 217-in frictional engagement at this in-.

stance with the fan support member 231will be rotated toward itsposition illustrated in Figure 6. In other w'ords, nut 217 will be movedtoward its unlocked position. If the bimetal 221 is still hot at thistime, nut 217 will immediately be retutned to its position of frictionalengagement with the fan support member 231; the structure will onceagain, therefore, be 'locked up when the pulley means 204 once againoverspeeds the fan support member 231 I As previously noted, the bimetal221 will not of itself have suflicient strength to move nut 217 out ofengagement with fan support member 231 because of the selflocking effectof the frictional engagement between nut 217 and support member 231.However, if bimetal 221 is sufliciently cool, when the support member231 overspceds the pulley member 204, as the nut 217 begins to moveawayfrom support member 231, bimetal 221 will continue this movement. Theparts will then assume the position illustrated in Figure 6 and thesupport member 231 with the fan assembly 236 will once again windmill.It should also be noted that if bimetal 221 should break, nut 217 willdrift rearwardly into engagement with support member 231 so that thedevice will remain in its locked-up condition.

The initial tension of bimetal 221 may be varied by loosening nut 224 onstud 233, and sliding stud 223 in the appropriate direction within theaccurate slot 28 formed in cup 24. Upon tightening of the nut'224, thebimetal 221;will operate with modified characteristics, as will beobvious to those skilled in the art. It will therefore be seen that thedevice of the pres ent invention permits desired, controlled operationof the fan with certainty and yet at a minimum expense. It should benoted that, particularly with respect to the preferred forms of theinvention as illustrated in Figures 1 through 3, and in Figures 6 and 7,that the pump shaft of-the vehicle as used in present day automotivevehicles need not be modified at all to accommodate the device of thisinvention. In distinction, the device of the present invention,particularly in the form illustrated in those figures may be constructedas a unit assembly-comprising the pulley with support member 9 and theelements supported thereby-and readily attached to the pump shaftemployed in conventional automotive vehicles in exactly the same manneras now employed to eifect the installation of the conventional fanassembly. When so attached the device is ready for immediate operation.In addition is should also be noted that in view'of the self-lockingarrangement of the screw threads employed in all forms of the devicedescribed, the nut 17 of Figure 1 (or the comparable mechanism in theother embodiments) will move rearwardly to lock up the fan and keep itoperating even if the bimetals should break. This is a ,fail safearrangement, and under those conditions the. fan would be continuouslyoperated until thedevice was repaired. It is also important to noticethat the arrangement of the parts is such that the temperature at whichthe fan is to be locked up may be varied by a very simple mechanismwhich is readily accessible, no special tools to efiect this adjustmentbeing required.

While certain preferred embodiments of the invention have beenspecifically disclosed, it is understood that the invention is notlimited thereto, as many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpretation within the terms of the following claims.

I claim:

1. In a control system, the combination comprising rotatable drivemeans, driven means co-axially disposed in relation to said drive meansnormally rotatable relative thereto, means to clamp said driven means tosaid drive means comprising a pair of relatively rotatable cammingmembers one of which is adapted to engage said driven means and effectthe aforementioned clamping action, thermally responsive means carriedby said drive means constructed and arranged to eifect relative ,meansextending through 10 rotation between said camming members andefiectengagement of said one camming member with said driven means, andmeans constructed and arranged to vary the temperature at which saidthermally responsive means operate.

2. The device defined in claim 1 in which said thermally responsivemeans comprise a bimetallic member 'and in which said means to vary thetemperature at which said thermally responsive means operate comprisesmeans to change the position of one portion of said bimetallic member.

3. In a fan control system, the combination comprising pulley meansadapted to be rotatably driven, first threaded means rotatable with saidpulley means, second threaded means mounted upon said first threadedmeans for rotational and longitudinal movement relative thereto, fansupport means disposed between a surface on said pulley means and asurface on one of said threaded means, a fan blade assembly carried bysaid fan support means, means defining openingsextending through saidfan blade assembly, stud means extending through said openings fixedlymounted to said fan support means having portions within said openingssmaller than said openings whereby limited rotational movement of saidfan blade assembly relative to said fan support means is permitted, andbimetallic means to efi'ect relative rotation between said first andsecond threaded means constructed and arranged to effect engagementbetween said one surface on one of said threaded means and said fansupport means to eifect clamping of said fan support means between saidone surface on one of said threaded means and said pulley means surfacewhereby -to effect common rotation of said pulley means and said fanblade assembly.

4. The device defined in claim 3 in which said first threaded means isformed as an integral extension of said pulley means.

5. The device defined in claim 3 in which said bimetallic meanscomprises a spirally wound bimetal, and in which means are provided tochange the initial tension of said spirally wound bimetal.

6. The device defined in claim 3 in which said pulley means is providedwith an extension, said fan support means being carried by saidextension, and inwhich said first threaded means is formed as anintegral part of said extension.

' 7. In a fan control system, the combination of pulley means adapted tobe rotatably driven, extension means carried by said pulley means, firstthreaded means formed on said extension means, second threaded meansmounted upon said first threaded means for rotational and longitudinalmovement relative thereto, fan support means disposed upon saidextension means between a surface of,

said pulley means and a surface on one of said threaded means andnormally rotatable relative to said extension means, a fan bladeassembly carried by said fan support means, means defining a pluralityof curved openings extending through said fan blade assembly, stud saidopenings fixedly mounted to said fan support means having portionswithin said openings smaller than said openings whereby limited rotationof said fan blade assembly relative to said fan support means ispermitted, and thermally responsive means to effect relative rotationbetween said first and second threaded means constructed and arranged toefiect engagement between said one surface on one of said threaded meansand said fan support means to effect clamping of said fan support meansbetween said one surface on one of said threaded means and said pulleysurface whereby to eifect common rotation of said driven pulley and saidfan blade assembly.

8. The device defined in claim 7 in which said thermally responsivemeans comprises a spirally wound bimetal and in which means are providedto vary the initial tension of said spirally wound bimetal.

9. In a fan, control system, the combination of pulley means adapted. tobe rotatably driven, extension means supported by said pulley means,first threaded means formed on said extension means, second threadedmeans mounted in engagement with said first threaded means forrotational and longitudinal movement relative thereto, fan support meansdisposed upon said extension means between a surface on said pulleymeans and a surface on one of. said threaded means and normallyrotatable relative to said extension means, a fan blade assembly fixedlymounted to said fan support means, and thermally responsive means toefiect relative rotation. between said first and second threaded meansconstructed and arranged to efiect engagement between said surface onone of said threaded means and said fan support means to efiect clampingof said fan support means between said surface on one of said threadedmeans and said surface on said pulley means whereby to efiect commonrotation of said pulley means and said fan blade assembly.

10. Fan control means comprising rotatable drive. means, extension meanssupported by said drive means for rotation therewith, first threadedmeans formed on said extension means, driven means supported upon saidextension means and normally rotatable relative thereto,

second threaded means in engagement with said first threaded means andmovable relative thereto to a first position in engagement with saiddriven means to effect the connection of said driven means to said drivemeans and toa second position spaced from said driven means todisconnect said driven means from said drive means, said driven meansbeing constructed and arranged to elfect movement of said secondthreaded means toward said' first position upon initial engagementbetween said driven means and said second threaded member, and thermallyresponsive means to efifect said initial engagement between said drivenmeans and said second threaded member.

11. The device defined in claim 10 in which said driven means comprisefan support means and fan'blade assembly means mounted thereon forrotation therewith.

12. The device defined in claim 10 in which said driven means comprisefan support means and fan blade assembly means mounted thereon, and inwhich said fan blade assembly means are provided with elongated slots.through which fastener means extend to provide a lost motion connectionbetween said fan blade assembly means and said fan support means.

13. The device defined in claim 10 in which said ther-' mally responsivemeans comprise bimetallic means, and in which means are provided to varythe operating characteristics ofsaid thermally responsive means.

14. Fan control mechanism comprising rotatable drive means, extensionmeans supported by said drive means.

12 for rotation therewith, first threaded means integrally formed onsaid extension means, driven means supported upon said extension meansand normally rotatable relative thereto, second threaded means inengagement with said first threaded means and movablerelative thereto toa first position in engagement with said driven means to effect theconnection of said driven means to said drive means and to a secondposition spaced from said driven means to disconnect said driven meansfrom said drive means, said driven means being constructed and arrangedto effect movement of said second threaded means toward said firstposition upon initial engagement between said driven means and saidsecond threaded member, a generally cup-shaped member carried by saidextension means for rotation therewith, thermally responsive means,means connecting said thermally respontive means to said cup-shapedmember, means connecting said thermally responsive means to said secondthreaded member, said thermally responsive means being constructed. andarranged to rotate said second threaded member relative to said firstthreaded member to efiect said initial engagement between said drivenmeans and said second threaded member, said means connecting saidthermally responsive means to said cup shaped member being constructedand arranged to effect changes in the operating characteristics of saidthermally responsive means.

15. The device defined in claim 14 in which said extension means areformed of phenolic resin material, and in which said thermallyresponsive means comprise a spirally wound bimetallic member.

16'. The device defined in claim 14 in which said driven means aredisposed upon said extension means intermediate said first threadedmeans and said drive means, and in which resilient means are disposedbetween said driven means and said drive means.

References Cited in the file of this patent UNITED STATES PATENTS936,190 Tuckfield Oct. 5, 1909 1,598,677 Donning Sept. 7, 1926 1,770,419McGrath July 15,. 1930; 1,940,090 Hetherington Dec. 1 9 1933' 2,005,468Modine June 1-8, 1935 2,381,567 Bonham Aug. 7, 1945; 2,459,377 HallinanJan. 18,. 1949 2,603,420 Tacchi July 15, 1952'; 2,740,388 Bennorth Apr.3, 19-56 FOREIGN PATENTS 163L440 Great Britain May 13, 1921- 593,596-Germany Mar. 6, 1934 831,712 France p r v June I3, 1935

